Additional hardpoints would require the ribs to be removed and additional higher load bearing ribs to be installed. The additional weight would have some effect on performance but not too much. This also depends of which ribs. So stressing will most probably slow down the work. However the current scenario of dual rack is much better as the original hardpoints was probably design to carry heavier payload so carrying two sd10 or other air to air missiles would probably be no issue. Drag may have to be checked
Conformal fuel tanks would be so the way to go